(1) Field of the Invention
The present invention relates to the field of gamma cameras used in the area of nuclear medicine. More specifically, the present invention relates to the field of collimator exchange mechanisms for exchanging collimator devices that are used in conjunction with gamma cronera detector heads in clinical imaging sessions.
(2) Prior Art
Nuclear or scintillation cameras (also called gamma cameras) are responsive to radiation emitted from a radiopharmaceutical injected into a patient during an imaging study. A given radiopharmaceutical is typically selected that will target a particular organ or tissue of interest. In computed tomography studies, a detector head (or pair) revolves around the patient and collects the emissions at various angles in order to generate an image of the targeted organ or tissue. In total body studies the detectors may translate at a fixed or variable attitude along the patient. In ECT studies, the image data collected at each angle is merged together into a database that is representative of a three dimensional image of the targeted organ or tissue by a mathematical procedure called reconstruction tomography. The image data collection and tomography is performed by a computer process and a computer system and the resultant images may be displayed in a variety of fashions on a computer controlled display screen. The above process is called an Emission Computed Tomography study or ECT study. Gamma camera detectors are also used in many types of studies which do not employ tomography for image generation, such as total body studies.
Each detector head of a gamma camera utilizes a collimator which is placed in front of the detector mechanism that responds to the incident emissions. The collimator is a device for collimating the incident radiation emissions and for filtering out certain types of unwanted radiation emissions. A collimator is typically manufactured from lead material and is composed of an array of parallel tubes and as such resembles a lead "honey comb." A collimator may weigh from 100 to 250 pounds or more individually and each is mounted on the receiving end of the gamma camera detector to cover the imaging surface.
Collimators have particular characteristics that are most suited to the patient study and the energy of the radiation emissions from the ingested radiopharmaceutical. For instance, some collimators are better suited for gamma camera studies of a given energy range, or a given emission exposure duration or a given radiopharmaceutical. As such, there is a great need to exchange collimators associated with the detector heads for different ECT or total body studies. Moreover, as different radiopharmaceuticals are used for different gamma camera studies, different collimators are often needed and must be installed by a technician. Further, each collimator must be securely fastened to the detector head during gamma camera studies to prevent collimator separation from the imaging surface as the detector heads revolve or rotate. Clearly, it would be advantageous, then, to provide an automated mechanism for quickly and correctly exchanging collimators associated with the camera detectors in between gamma camera studies. The present invention provides such capability.
In the prior art, collimators were manually exchanged and were mounted on trays, trolleys, or carts that were manually positioned or aligned adjacent to a detector head and fastened manually to the camera. This involved a time consuming operation and required a great deal of manual exertion due to the extreme weight and awkward size of the collimators. The exchange process often could not be performed by the usual gamma camera technicians and therefore the exchange was additionally time consuming because additional personnel were required to perform the manual exchange. Not only did the manual exchange require additional time and personnel (adding to the expense of the gamma camera study), but by using manual alignment and exchange means the collimators suffered the risk of being installed improperly or misaligned. These factors contribute to the quality, reproducibility and precision of data collected (and the resultant image) during a gamma camera study. Therefore, it would be advantageous to provide a mechanism and method that automatically exchanged collimators for a gamma camera detector head without requiring extensive operator interaction. It would also be advantageous to automate the exchange procedure in order to insure that collimators are properly selected, aligned and installed. The present invention provides for such functionality.
Some prior art mechanisms are employed to automatically exchange a collimator with a single detector head. For example, U.S. Pat. No. 5,146,094 issued to Stark on Sep. 8, 1992, provides an automated mechanism wherein one collimator may be exchanged with one detector head. The detector head must be lowered and moved in alignment with a tray of collimators and a collimator may be directly loaded onto (or removed) the detector via a groove installed within the detector head. Other prior art devices, as described in U.S. Pat. Nos. 3,982,133 (issued to Jupa et al.); 4,129,784 (issued to Tschunt et al.); and 4,109,155 (issued to Tschunt et al.), directly exchange a single collimator for a single detector head using a swivel mechanism. However these prior art devices do not account for dual head gamma cameras and as such do not provide the means for exchanging two collimators at the same time for a camera system with a dual detector head arrangement. It would be advantageous to provide an exchange mechanism that operates to exchange, simultaneously, collimators for a dual head gamma camera system without requiring manual means or extensive operator intervention. The present invention provides such mechanisms and capabilities.
Accordingly, it is an object of the present invention to provide a more efficient nuclear medicine gamma camera system. An object of the present invention is to provide mechanisms and means for automatically removing and installing a collimator on a detector head without requiring manual exertion or manual operation. It is another object of the present invention to provide an automated exchange mechanism for simultaneously exchanging collimators on a dual head gamma camera system without requiring extensive operator interaction. It is further an object of the present invention, given a pair of collimators already mounted on a pair of detector heads, to provide a mechanism and method for allowing an operator to select an input pair of collimators for use in a gamma camera study and for automatically exchanging the pair of collimators mounted on the detector heads with the selected pair without further operator intervention. It is yet another object of the present invention to provide such an exchange mechanism that may perform its exchange operations within the spatial area of the gantry structure of the gamma camera system in order to reduce the amount of floor space required for the exchange operation and required of the resultant gamma camera system. It is further an object of the present invention to provide a collimator removal and installation mechanism that prevents collimator separation from the detector head during a gamma camera imaging session (e.g., clinical study).
It is further an object of the present invention to provide a gamma camera system that employs a collimator exchanger mechanism that may simultaneously and automatically exchange collimators of a dual detector head arrangement. These and other objects of the present invention not specifically mentioned above will become clear upon review of the discussions of the present invention to follow.